The proposed research is designed to study the regulation of lipid metabolism in bacteria as a model system. Our approach to this problem will entail characterization of E. coli mutants defective in fatty acid metabolism. We plan to study extensively the following mutants: (1) Mutants which are constitutive for the synthesis of the fatty acid degradative enzymes; (2) mutants which are defective in long-chain fatty acid catabolism; (3) mutants which are defective in medium-chain fatty acid catabolism; (4) mutants which are defective in even-chain fatty acid catabolism; and (5) mutants which are defective in odd-chain fatty acid metabolism. Some of these mutants may owe their phenotype to lesions in regulatory genes and others to lesions in structural genes. Genetic, physiological, and biochemical studies will be performed on these mutants in an attempt to understand the molecular basis for their defect. These studies should further our understanding of the mechanism(s) by which fatty acid metabolism is regulated.